1H NMR study of the catalytic system (rac-Me2Si(2-Me,4-PhInd)2ZrCl2— polymethylalumoxane)—triisobutylaluminum

The products of the reactions of polymethylalumoxane (MAO) with triisobutylaluminum (TIBA), rac-Me₂Si(2-Me,4-PhInd)₂ZrCl₂ (1) with MAO (1 + MAO), and (1 + MAO) + TIBA were studied by ¹H NMR at different molar ratios of the components. When the ratio Al_TIBA/Al_MAO is ∼6, the reaction between MAO and TIBA involves the replacement of the methyl group of MAO by isobutyl groups and the formation of isobutylmethylalumoxane or mixed isobutylmethylalumoxane structures. When the TIBA content in the system increases to 30 mol.%, these structures are rearranged to form products with a low degree of association. With the equimolar ratio of the reactants, the main reaction products are tetraisobutylalumoxane and polyisobutylalumoxane. The 1 + MAO system with the molar ratio Al_MAO/Zr = 50 affords a MAO-bonded monomethyl monochloride derivative L₂ZrCl-μ-Me]^δ+MAO]^δ−. An increase in this ratio to 150 produces intermediate binuclear complexes L₂ZrCl-μ-Me-MeZrL₂]⁺MAO]⁻ and Me₂Al-(μ-Me)₂-ZrL₂]⁺MAO]⁻. The addition of TIBA induces the replacement of the ZrMe groups by isobutyl groups at the first step of the interaction and formation of nonidentified reaction products at the subsequent steps. __________ Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 934–940, April, 2005.